It's not so much that malloc can fail, but that you're likely to get whacked by OOM before you run out of address space on linux. To get malloc to return a NUL

It's not so much that malloc can fail, but that you're likely to get whacked by OOM before you run out of address space on linux. To get malloc to return a NULL, you would have to be allocating more than 4Gb of memory on a 32 bit system, the system has to have no swap, and you have to not have used any of the memory between the last physically available memory, and the memory allocated by the chunk that takes you over the 4Gb limit. Anything else gets you SIGKILLed.